Door Knob for Baby

My well-meaning mother-in-law says the dumbest things sometimes.  She was walking my 8 month old son around my living room suggesting items that I ought to buy for him to stimulate his interest or abilities.  According to her, he needs a swing, a walker, a jumper, and a myriad of toys.  This goes on for hours like a broken record each time she visits.  The suggestions are too numerous to be taken seriously, so I try to have a sense of humor about them.  Sometimes, she makes it REALLY easy to laugh at them.  At one point, she walked him past the front door and he reached out to touch the shiny brass door knob.  She allowed him to stop there and he spent a minute or two tapping and twisting at the knob.  She turned to me and said, "You need to buy him a door knob like this one, because he is fascinated by it."  I said, "He already has one."  She said with wonder, "He does?"  I said, "Yes, THAT IS HIS door knob."